If you maintain a distribution package, or app bundle, or container image, it’s handy to know when components you use in it have new releases.
There is a really useful service Anitya that resides on release-monitoring.org. It watches almost 20 thousand projects for new releases and notify about them.
I maintain several packages in Fedora and the Fedora Project already makes it really convenient for me. It uses Anitya and opens a new bug against your package every time there is a new upstream release which I close once I update the package. But not every project gives you this service.
I also maintain several apps on Flathub which doesn’t provide such a service (yet). And it’s even more important to know about new upstream releases because besides the apps themselves I also have to maintain their dependencies which are not available in runtimes. Especially Evolution has quite a few of them.
Anitya gives you an API, so you can write your own service that will be checking with Anitya. But I’m a lazy person and why to write something that already exists, right? The Fedora Project has a web app called Fedora Notifications which can send notifications of all sorts of events to your email or IRC. You don’t have to be a Fedora package maintainer or anyhow involved in the Project. All you need is a Fedora account (FAS) to log in.
You pick Email Notifications (or IRC, whichever you prefer), click Create New Filter, then you pick Anything regarding a particular “upstream project” rule, and add projects you want to monitor separated by commas. Then click Add this rule and you’re good to go. This is what my rule for components I maitain in Flathub looks like:
You’ll be getting notifications of new upstream releases to your email and it’s up to you how you’ll act on them. I typically check what kind of release it is, if there are any security or important bug fixes. I try to release those ASAP. Otherwise I plan them for future app releases and test with them beforehand.
I can imagine that there can be a nice automation built on the top of the Anitya API. If it detects a new release, it updates the manifest, triggers a build, and sends you info how it went. Maybe one day 🙂
Brno hat 
When I attempt to access the notifications app at https://apps.fedoraproject.org/notifications/ using my ordinary FAS account, I get a “401 unauthorized” page. So apparently this service is not available to ordinary users.